MR features of the denervated tongue in radiation induced neuropathy

The MR features of the denervated tongue have been described following nerve injury from radical neck dissection and tumour invasion. The purpose of the study was to determine whether similar features are present in the tongue following radiation induced neuropathy (RIN). The clinical records and MR images of 12 patients with RIN of the hypoglossal nerve were reviewed retrospectively. T1 weighted SE images were performed in 12, T2 weighted TSE images in 11, fat suppressed images in 10 and contrast enhanced T1 weighted images in nine patients. The denervated tongue revealed "oedemalike" changes in five, fatty infiltration in six, atrophy in 11 and pseudohypertrophy in one patient. Abnormal enhancement was not identified, and in five patients the signal intensity was normal on all sequences. The oedemalike changes, fatty infiltration and normal signal intensity were seen 2-48, 2-48, and 6-63 months, respectively, after the onset of RIN. In conclusion, there was no discernible relationship between the duration of RIN and the MR appearance of the denervated tongue. Oedemalike changes, previously described in the acute/subacute phase of denervation, were also seen in long-standing disease and there was no associated abnormal enhancement in any case. Furthermore, the signal intensity may be normal, the MR diagnosis relying on asymmetry of the size of the tongue. It is postulated that radiation causes incomplete and ongoing damage of the nerve, the course of which is unpredictable.